Among display devices, such as liquid crystal display devices, which are under development, there have been touch-panel-integrated display devices each having a touch panel (area sensor) function that makes it possible to detect the position of contact of an input pen with the panel surface.
Mainstream examples of conventional touch-panel-integrated display devices include a resistive type (which, when pressed, detects the position of an input through contact between upper and lower conductive substrates) and a capacitance type (which detects the position of an input by detecting a change in capacitance of a place touched).
Meanwhile, in recent years, the development of a liquid crystal display device having a light sensor element such as a photodiode or a phototransistor provided in each pixel (or in each unit of a plurality of pixels) within an image display region has been advanced (e.g., see Patent Literature 1). By thus having a light sensor element built in each pixel, an ordinary liquid crystal display device can fulfill a function as an area sensor (specifically, a scanner function, a touch panel function, etc.). That is, by such light sensor elements fulfilling a function as an area sensor, a display device integrated with a touch panel (or with a scanner) can be achieved.